I tried using interface to get the owner address from another NFT smart contract (ERC721) like this:

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.13;

interface INft {
    function owner() external view returns (address); //doesn't work
    function name() external view returns (string calldata); //works
    function ownerOf(uint256 tokenId) external view returns (address); //works
}

contract Test {
    //doesn't work
    function getNftProjectOwner (address _nft) external view returns (address){
        return INft(_nft).owner();
    }
    //works
    function getNftProjectName (address _nft) external view returns (string memory){
        return INft(_nft).name();
    }
    //works
    function getNftTokenOwner(address _nft, uint256 _tokenId) external view returns (address){
        return INft(_nft).ownerOf(_tokenId);
    }
    
}

So far all other external function call works except for the one that gets the nft smart contract owner address. Here's the reference from OpenZeppelin's Ownable.sol:

/**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

I also noticed that Ownable is an abstract contract and I'm wondering if I have declared it as an interface wrongly? I kept getting the error message "call to Test.getNftProjectOwner errored: execution reverted"